The field of art to which this invention pertains is the hydrocracking of a hydrocarbonaceous feedstock. Petroleum refiners often produce desirable products such as turbine fuel, diesel fuel and lube oil fractions as well as lower boiling hydrocarbonaceous liquids such as naphtha and gasoline by hydrocracking a hydrocarbon feedstock derived from crude oil, for example. Feedstocks most often subjected to hydrocracking are gas oils and heavy gas oils recovered from crude oil by distillation. A typical gas oil comprises a substantial portion of hydrocarbon components boiling above about 700xc2x0 F., usually at least about 50 percent by weight boiling above 700xc2x0 F. A typical vacuum gas oil normally has a boiling point range between about 600xc2x0 and about 1050xc2x0 F.
Hydrocracking is generally accomplished by contacting in a hydrocracking reaction vessel or zone the gas oil or other feedstock to be treated with a suitable hydrocracking catalyst under conditions of elevated temperature and pressure in the presence of hydrogen so as to yield a product containing a distribution of hydrocarbon products desired by the refiner. The operating conditions and the hydrocracking catalysts within a hydrocracking reactor influence the yield of the hydrocracked products. Although a wide variety of process flow schemes, operating conditions and catalysts have been used in commercial activities, there is always a demand for new hydrocracking methods which provide lower costs and higher liquid product yields. Conventionally, unconverted oil from a hydrocracking plant that was to be used for lube oil production would be fractionated at sub-atmospheric pressure which requires the heating of the hydrocarbon in a fired heater and the subsequent introduction into an expensive vacuum column.
U.S. Pat. No. 5,720,872 (Gupta) discloses a process for hydroprocessing liquid feedstocks in two or more hydroprocessing stages which are in separate reaction vessels and wherein each reaction stage contains a bed of hydroprocessing catalyst. The liquid product from the first reaction stage is sent to a low pressure stripping stage and stripped of hydrogen sulfide, ammonia and other dissolved gases. The stripped product stream is then sent to the next downstream reaction stage, the product from which is also stripped of dissolved gases and sent to the next downstream reaction stage until the last reaction stage, the liquid product of which is stripped of dissolved gases and collected or passed on for further processing. The flow of treat gas is in a direction opposite the direction in which the reaction stages are staged for the flow of liquid. Each stripping stage is a separate stage, but all stages are contained in the same stripper vessel. U.S. Pat. No. 5,114,562 (Haun et al) discloses a process wherein distillable petroleum streams are hydrotreated to produce a low sulfur and low aromatic product utilizing two reaction zones in series. The effluent of the first reaction zone is purged of hydrogen sulfide by hydrogen stripping and then reheated by indirect heat exchange. The second reaction zone employs a sulfur-sensitive noble metal hydrogenation catalyst.
U.S. Pat. No. 5,980,729 (Kalnes et al) discloses a hydrocracking process which utilizes a hot, high-pressure stripper.
U.S. Pat. No. 4,194,964 (Chen et al) discloses a process for the simultaneous distillation and hydrocracking of hydrocarbon feeds in a single vessel.
U.S. Pat. No. 6,096,191 (Kalnes) discloses a catalytic hydrocracking process wherein a hydrocarbonaceous feedstock and a liquid recycle stream having a temperature greater than about 500xc2x0 F. and saturated with hydrogen is contacted with hydrogen and a metal promoted hydrocracking catalyst in a hydrocracking reaction zone at elevated temperature and pressure to obtain conversion to lower boiling hydrocarbons.
The present invention is a catalytic hydrocracking process which provides lower costs and higher liquid product yields including lube oil. The process of the present invention provides an integrated method for the simultaneous production of various hydrocracked product streams including lube base oil.
In accordance with one embodiment the present invention relates to a process for hydrocracking a hydrocarbonaceous feedstock to produce lower boiling hydrocarbonaceous compounds which process comprises: (a) contacting the hydrocarbonaceous feedstock and hydrogen with a metal promoted hydrocracking catalyst in a hydrocracking zone at elevated temperature and pressure sufficient to obtain a substantial conversion to lower boiling hydrocarbons; (b) stripping the uncooled hydrocarbon effluent from the hydrocracking zone in a hot, high pressure stripping zone maintained at essentially the same pressure as the hydrocracking zone with a first hydrogen-rich gaseous stream to produce a first gaseous hydrocarbonaceous stream and a first liquid hydrocarbonaceous stream; (c) condensing at least a portion of the first gaseous hydrocarbonaceous stream and separating the same into a second liquid hydrocarbonaceous stream and a second hydrogen-rich gaseous stream; (d) recycling at least a portion of the second hydrogen-rich gaseous stream from step (c) to supply at least a portion of the hydrogen in step (a) and at least a portion of the first hydrogen-rich gaseous stream in step (b); and (e) stripping at least a portion of the first liquid hydrocarbonaceous stream to produce a third liquid hydrocarbonaceous stream comprising heavy lube base oil.
In another embodiment the present invention relates to a process for hydrocracking a hydrocarbonaceous feedstock to produce lower boiling hydrocarbonaceous compounds which process comprises: (a) contacting the hydrocarbonaceous feedstock and hydrogen with a metal promoted hydrocracking catalyst in a hydrocracking zone at elevated temperature and pressure sufficient to obtain a substantial conversion to lower boiling hydrocarbons; (b) stripping the uncooled hydrocarbon effluent from the hydrocracking zone in a hot, high pressure stripping zone maintained at essentially the same pressure as the hydrocracking zone with a first hydrogen-rich gaseous stream to produce a first gaseous hydrocarbonaceous stream containing hydrocarbonaceous compounds boiling at a temperature less than about 700xc2x0 F. and to produce a first liquid hydrocarbonaceous stream containing hydrocarbonaceous compounds boiling at a temperature greater than about 700xc2x0 F.; (c) condensing at least a portion of the first gaseous hydrocarbonaceous stream and separating the same into a second liquid hydrocarbonaceous stream and a second hydrogen-rich gaseous stream; (d) recycling at least a portion of the second hydrogen-rich gaseous stream from step (c) to supply at least a portion of the hydrogen in step (a) and at least a portion of the first hydrogen-rich gaseous stream in step (b); (e) stripping at least a portion of the first liquid hydrocarbonaceous stream to produce a third liquid hydrocarbonaceous stream comprising heavy lube base oil; and (f) fractionating at least a portion of the second liquid hydrocarbonaceous stream to produce a fourth liquid hydrocarbonaceous stream comprising light lube base oil.
Other embodiments of the present invention encompass further details such as types and descriptions of feedstocks, hydrocracking catalysts and preferred operating conditions including temperatures and pressures, all of which are hereinafter disclosed in the following discussion of each of these facets of the invention.